An aqueous viscosity modifier (sometimes referred to as “thickener” or “gelling agent”) is generally used in various fields, such as paints, adhesives and pressure-sensitive adhesives, foods, and cosmetics. By being added to various products, the aqueous viscosity modifier can increase viscosities of the products to impart various functions thereto. For example, an oil-in-water emulsified composition to be used for, for example, a drug, a quasi-drug, or a milky lotion serving as a cosmetic is generally changed in viscosity (e.g., thickening or gelation) using a viscosity modifier. This is because the change in viscosity results in various effects, such as an improvement in spread on a skin and achievement of a unique feeling. A degree to which the viscosity is changed greatly varies for each product. For example, the product is greatly thickened like a cream in some cases, or the viscosity is changed without a significant change in apparent viscosity like a face lotion in other cases.
In recent years, in the field of cosmetics, an “all-in-one cosmetic” has been attracting attention as a basic cosmetic. In general, as kinds of the basic cosmetic, there are given a face lotion, a milky lotion, a beauty serum, a cream, and the like, each of which plays a different role. Examples thereof include the following: the face lotion “delivers a moisturizing component to the stratum corneum”; the beauty serum “keeps moisture supplied by the face lotion and gives the skin a special nutrient to further enhance the moisturizing effect”; and the milky lotion or the cream “holds the moisture of the skin to recover the barrier function of the skin.” The “all-in-one cosmetic” is a very highly functional and convenient cosmetic that allows those roles to be covered by one cosmetic. The “all-in-one cosmetic” is in very high demand, and is also required by the market to have high performance.
The performance required of the gelling agent to be used for the “all-in-one cosmetic” is as follows: the gelling agent gives a characteristic gel needed for giving a satisfactory feeling of use, supplying moisture to the skin, and keeping moisture for a long period of time. Features of this gel include, for example, having elasticity for keeping a gel state when the gel is taken in a hand, and having softness for ease of spread on the skin. Further, a gel that is also less restricted in terms of its container is preferred, and for example, there is a demand for a gel that can be used even with a wide-mouth container with a lid or a spray bottle, without any problem. Particularly when contained in the wide-mouth container with a lid, a gel having such a self-leveling property that, when the gel is taken out with fingers to be taken in a hand, the remaining gel in the container spontaneously returns to a leveled state provides a fresh feeling and a sanitary feeling when next used, and hence tends to be highly evaluated by users. In addition, when contained in the spray bottle, a characteristic gel that is jetted like water through application of a shearing stress thereto by a spraying operation, and returns to a gel-like state on the skin is more highly evaluated by users as a functional and convenient cosmetic.
As gelling agents usable for cosmetics, for example, there are generally known: a natural gelling agent, such as carboxymethylcellulose or hydroxyethylcellulose; an alkali thickening type gelling agent of a type that thickens with an alkali, such as polyacrylic acid or a polyacrylic acid-containing copolymer; and a urethane-type gelling agent, such as urethane-modified polyether. Of those, as compared to other gelling agents, the urethane-type gelling agent has been produced in many kinds and frequently used for, for example, the following reasons: various kinds thereof can be freely produced; the urethane-type gelling agent can impart a variety of viscosities to products by being added thereto; and the urethane-type gelling agent is hardly affected by a pH or a salt (for example, Patent Documents 1 to 7).
Patent Document 1: JP 2014-523933 A
Patent Document 2: JP 2008-505232 A
Patent Document 3: JP 2007-217700 A
Patent Document 4: JP 2004-525995 A
Patent Document 5: JP 2000-239649 A
Patent Document 6: JP H11-199854 A
Patent Document 7: WO 2014/084174